fix: remove 'main' field from package.json to fix plugin loading (v0.2.1)

The 'main' field pointing to 'dist/main.js' was preventing Headlamp from properly loading the plugin. Headlamp expects main.js in the root directory of the plugin.

Changes:
- Removed 'main' field from package.json
- Bumped version to 0.2.1
- Created Artifact Hub metadata for 0.2.1
- Updated checksum: SHA256:bf0c1211b51df29d378ec9dabd2599cbff6f32fdc98bcae9807fe2ff5cf87a8a

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via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

headlamp-sealed-secrets/package.json

@@ -1,8 +1,7 @@
 {
   "name": "headlamp-sealed-secrets",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "description": "Headlamp plugin for Bitnami Sealed Secrets - manage encrypted Kubernetes secrets",
-  "main": "dist/main.js",
   "files": [
     "dist",
     "README.md",